This invention generally relates to the attachment of wheel speed sensors to axle housings for vehicle antilock braking systems. More specifically, this invention relates to an adjustable wheel sensor retention system with locking features.
Vehicle antilock braking systems have established widespread usage on cars and trucks. It is well known that maximum braking traction and vehicle directional stability is achieved when only a small degree of relative slippage is allowed between the vehicle tires and pavement. In order to control slippage, antilock braking systems establish servo-feedback control of the brake system to minimize slippage during braking. A typical system uses an antilock braking controller to determine incipient wheel slip and modulates brake pressure based on wheel speed information determined from wheel speed sensors located on each braked wheel axle assembly. Each wheel speed sensor is usually mounted to an axle housing in close proximity to an exciter (often referred to as a xe2x80x9ctone wheelxe2x80x9d), which is mounted to the wheel hub and rotates with the wheel. The wheel speed sensors may use various sensing principles such as magnetic reluctance, Hall effect or optics as known in the art. It is critical that the wheel speed sensors, particularly passive sensors such as the magnetic reluctance type, be located with a precise clearance or air gap relative to the exciter or tone wheel to generate a sufficient electrical signal for input to the controller. The air gap between the sensor and exciter must typically be adjusted during the vehicle final assembly to assure the required air gap because of the various component and assembly tolerances within the axle assembly. The initial adjustment of the air gap and retention of the air gap calibration has proven difficult or costly with known wheel speed retention assemblies. Moreover, once the desired clearance is established, it is necessary that the air gap remain fixed during operation, despite the severe operating environment to which the sensor is exposed.
Accordingly, this invention provides for a speed sensor retention bushing and assembly for a vehicle anti-lock braking system which overcomes the problems and disadvantages of the conventional techniques in the art. The invention also provides for a self-adjusting type retention assembly with a locking feature which prevents inadvertent movement of the sensor during assembly, repair or use.
Briefly, the invention includes a resilient retention bushing with a locking prong which is deflected and spring loaded to engage the sensor when the sensor is installed. The locking prong resists movement of the sensor relative to the bushing. The deflected locking prong also resists retraction of the bushing from the mounting block which receives the sensor and bushing.
Further objects, features and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.